Angiotensin II (Angll) and its G protein-coupled AT1 receptor play critical roles in mediating cardiovascular diseases such as hypertension, atherosclerosis, and restenosis after vascular injury. It is widely believed that Angll promotes these diseases by inducing vascular remodeling that involves hypertrophy, hyperplasia, and migration of vascular smooth muscle cells (VSMCs). It has been shown that transactivation of an ErbB family receptor, EGF receptor (ErbB1/EGFR), is essential for VSMC hypertrophy and migration by Angll. However, the precise signal transduction mechanism by which Angll transactivates EGFR/ErbB1 and whether other ErbBs are also required for Angll function remains unclear. Recent studies suggest an involvement of a metalloprotease-dependent ErbB family ligand production in the transactivation. Thus, our central hypothesis is that an AT1-derived second messenger promotes activation of ADAM metalloprotease leading to ErbB receptors transactivation and subsequent remodeling in VSMCs. Our past and current preliminary studies strongly support our central hypothesis. Therefore, the specific aims of this application are designed to identify the signaling mechanism(s) and functional significance of the metalloprotease/ErbB activation by Angll in VSMCs. The specific aims of the study are: Aim 1. To test the hypothesis that G protein and second messengers are involved in metalloprotease activation through the AT1 receptor. Aim 2. To test the hypothesis that ADAM metalloprotease is activated by a mechanism involving ADAM cytoplasmic tail and a cytosolic tyrosine kinase. Aim 3. To test the hypothesis that several ErbB ligands are produced by Angll and mediate Angll-induced transactivation of ErbB receptors. Aim 4. To test the hypothesis that the transactivation of ErbB receptors is required for hypertrophy and migration of VSMCs induced by Angll. Accomplishment of these specific aims will not only give us a better understanding of the critical molecular mechanism underlying vascular remodeling stimulated by Angll but will also contribute to development of novel treatment strategies toward cardiovascular diseases.